#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

int main()
{
    double n;
    cin >> n;
    double l = -100, r = 100;
    while(r - l > 1e-8)
    {
        double mid = (l + r) / 2;
        if(mid * mid * mid >= n) r = mid;
        else l = mid;
    }
    printf("%.6lf\n", l);
    return 0;
}